TD1482 Schematic ( PDF Datasheet ) - Techcode

Teilenummer	TD1482
Beschreibung	1.6A 23V Synchronous Rectified Step-Down Converte
Hersteller	Techcode
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Gesamt 14 Seiten T  echcode® DATASHEET       1.6A 23V Synchronous Rectified Step-Down Converte TD1482 General Description  Features    The TD1482 is a monolithic synchronous buck •   1.6A Output Current regulator. The device integrates two 130mΩ •   Wide 4.75V to 23V Operating Input Range MOSFETs, and provides 1.6A of continuous load •   Integrated 130mΩ Power MOSFET Switches current over a wide input voltage of 4.75V to 23V. •   Output Adjustable from 0.923V to 20V Current mode control provides fast transient •   Up to 93% Efficiency response and cycle-by-cycle current limit. •   Programmable Soft-Start An adjustable soft-start prevents inrush current at turn-on, and in shutdown mode the supply current •   Stable with Low ESR Ceramic Output Capacitors drops to 1µA. •   Fixed 340KHz Frequency This device, availablein an SOP8 package, •   Cycle-by-Cycle Over Current Protection provides a very compact solution with minimal external •   Input Under Voltage Lockout components.  Applications  •   Distributed Power Systems •   Networking Systems •   FPGA, DSP, ASIC Power Supplies •   Green Electronics/ Appliances • Notebook Computers Package Types                      Figure 1. Package Types of TD1482  October,  20,  2010.                                                        Techcode  Semiconductor  Limited                                                  www.techcodesemi.com  1  T  echcode® DATASHEET       1.6A 23V Synchronous Rectified Step-Down Converte TD1482 Electrical Characteristics(Cont.)  VIN = 12V, Ta = 25℃  unless otherwise specified.  Parameters Input Under Voltage Lockout Threshold Input Under Voltage Lockout Threshold Hysteresis Soft-Start Current Soft-Start Period Thermal Shutdown * Symbol Test Condition VIN Rising VSS = 0V CSS = 0.1µF Min. Typ. Max. 3.80 4.10 4.40 210 Unit V mV 6 µA 1 ms 5 160 °C Typical Performance Characteristics  Figure 4. Steady State Test  Figure 5. Startup through Enable    October,  20,  2010.                                                        Techcode  Semiconductor  Limited                                                  www.techcodesemi.com  6  6 Page T  echcode® DATASHEET       1.6A 23V Synchronous Rectified Step-Down Converte TD1482 The system has one zero of importance, due to the compensation capacitor (C3) and the compensation resistor (R3). This zero is located at:   The system may have another zero of importance, if the output capacitor has a large capacitance and/or a high ESR value. The zero,due to the ESR and capacitance of the output capacitor, is located at: Determine the C3 value by the following equation:   Where R3 is the compensation resistor. 3. Determine if the second compensation capacitor (C6) is required. It is required if the ESR zero of the output capacitor is located at less than half of the switching frequency, or the following relationship is valid:   In this case (as shown in Figure 14), a third pole set by the compensation capacitor (C6) and the compensation resistor (R3) is used to compensate the effect of the ESR zero on the loop gain. This pole is located at:   The goal of compensation design is to shape the converter transfer function to get a desired loop gain. The system crossover frequency where the feedback loop has the unity gain is important. Lower crossover frequencies result in slower line and load transient responses,while higher crossover frequencies could cause system instability. A good rule of thumb is to set the crossover frequency below one-tenth of the switching frequency. To optimize the compensation components, the following procedure can be used. 1. Choose the compensation resistor (R3) to set the desired crossover frequency. Determine the R3 value by the following equation:   Where fC is the desired crossover frequency which is typically below one tenth of the switching frequency. 2. Choose the compensation capacitor (C3) to achieve the desired phase margin. For applications with typical inductor values, setting the compensation zero, fZ1, below one-forth of the crossover frequency provides sufficient phase margin.    If this is the case, then add the second compensation capacitor (C6) to set the pole fP3 at the location of the ESR zero. Determine the C6 value by the equation:   External Bootstrap Diode An external bootstrap diode may enhance the efficiency of the regulator, the applicable conditions of external BST diode are: z VOUT=5V or 3.3V; and z Duty cycle is high: In these cases, an external BST diode is recommended from the output of the voltage regulator to BST pin, as shown in Fig.14   Figure14.Add Optional External Bootstrap Diode to Enhance  Efficiency  The recommended external BST diode is IN4148, and the BST cap is 0.1~1μF.   October,  20,  2010.                                                        Techcode  Semiconductor  Limited                                                  www.techcodesemi.com  12  12 Page
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TD1482	1.6A 23V Synchronous Rectified Step-Down Converte	Techcode
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TD1484A	3.2A 23V Synchronous Rectified Step-Down Converte	Techcode

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